Field of the Invention
The present invention relates to a focus control apparatus that controls an autofocus (AF) in an image capturing apparatus.
Description of the Related Art
One image capturing apparatus performs an AF control that controls a position of a focus lens in an image capturing apparatus focused on an object. Another image capturing apparatus includes a memory for storing electronic cam data that represents a position of a focus lens focused on each of a plurality of object distances for each zoom position in an image capturing optical system that can provide a zoom (magnification variation). This image capturing apparatus can continuously focus on an object at the same distance or fix a focus position even when the zoom position is changed, through zoom tracking that controls the focus lens position by utilizing the electronic cam data in zooming.
Even when the focus position is fixed, if the orientation of the image capturing apparatus changes or the image capturing apparatus vibrates, the focus lens position changes and the blur (defocus) occurs due to the mechanical backlash. The blur also occurs due to the thermal expansions and contractions of the image capturing apparatus or the image capturing apparatus.
In order to correct these blurs, it is necessary to correct the position of the focus lens according to an amount of the blur. However, the blur amounts caused by the mechanical backlash and the thermal change depend on the individual image capturing optical system and the individual image capturing apparatus, and the blur may not be well corrected even when the focus lens position is corrected with a uniform correction amount.
Japanese Patent Laid-Open No. (“JP”) 2014-106324 discloses an image capturing apparatus that previously measures and stores a blur amount caused by an orientation difference between the starting time and the AF time in the image capturing apparatus, and controls a focus lens position so as to correct the blur amount according to the orientation detected in the actual AF. In addition, JP 2012-128314 discloses an image capturing apparatus that provides an AF control that corrects a blur caused by a thermal change detected by the temperature detector.
However, the image capturing apparatus disclosed in JP 2014-106324 needs a detector configured to detect the orientation of the image capturing apparatus. On the other hand, in the image capturing apparatus disclosed in JP 2012-128314, an object different from the original object may be focused (or the object replacement occurs) due to the AF control configured to correct the blur caused by the thermal change.